[Rev 03] RFR: 8088198: Exception thrown from snapshot if dimensions are larger than max texture size

[Frederic Thevenet]

On Sun, 26 Jan 2020 11:40:06 GMT, Frederic Thevenet <github.com+7450507+fthevenet at openjdk.org> wrote:

>>> the `WriteableImage` used to collate the tiles and the tiles returned from the `RTTexture` have different pixel formats (`IntARGB` for the tile and `byteBGRA` for the `WriteableImage`).
>> 
>> Where did you see these?
>> 
>>> Unfortunately it seems the only way to choose the pixel format for a `WritableImage` is to initialize it with a `PixelBuffer`, but then one can no longer use a `PixelWriter` to update it...
>> 
>> You can update it with `PixelBuffer#updateBuffer`. I think that you will want to pass the stitched tile as the dirty region.
> 
>> 
>> 
>> > the `WriteableImage` used to collate the tiles and the tiles returned from the `RTTexture` have different pixel formats (`IntARGB` for the tile and `byteBGRA` for the `WriteableImage`).
>> 
>> Where did you see these?
> 
> Simply by watching the value of  `tile.getPixelReader().getPixelFormat()` and `wimg.getPixelWriter().getPixelFormat()` before doing the copy at https://github.com/openjdk/jfx/blob/4bc4417356ebd639567d315257a6bbe11344d9c2/modules/javafx.graphics/src/main/java/javafx/scene/Scene.java#L1315
>> 
>> > Unfortunately it seems the only way to choose the pixel format for a `WritableImage` is to initialize it with a `PixelBuffer`, but then one can no longer use a `PixelWriter` to update it...
>> 
>> You can update it with `PixelBuffer#updateBuffer`. I think that you will want to pass the stitched tile as the dirty region.
> 
> Thanks. I'll look into it.

> 
> 
> > profiling a run of the benchmark shows that a lot of time is spent into `IntTo4ByteSameConverter::doConvert`
> 
> This is a bit naive, but what if you parallelize the code there? I didn't test that this produces the correct result, but you can try to replace the loops with this:
> 
> ```
> IntStream.range(0, h).parallel().forEach(y -> {    
>     IntStream.range(0, w).parallel().forEach(x -> {
>         int pixel = srcarr[srcoff++];              
>         dstarr[dstoff++] = (byte) (pixel      );   
>         dstarr[dstoff++] = (byte) (pixel >>  8);   
>         dstarr[dstoff++] = (byte) (pixel >> 16);   
>         dstarr[dstoff++] = (byte) (pixel >> 24);   
>     });                                            
>     srcoff += srcscanints;                         
>     dstoff += dstscanbytes;                        
> });                                                
> ```

I don't think this works as it is, as all threads race to increment `srcoff` and `dstoff`.

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PR: https://git.openjdk.java.net/jfx/pull/68